Previous studies indicate that cell-mediated immunity (CMI) plays a significant role in the pathophysiology of periodontal disease. These studies have measured various cell-mediated immune responses of peripheral blood leukocytes to dental plaque antigens. It appears that the distribution of the local gingival population of leukocytes is different from that found in peripheral blood. Additionally, the local gingival environment is probably rich in factors known to modify CMI, namely, antigen, antibody, and antigen-antibody complexes. Therefore, the cell-mediated response of gingival crevice lymphocytes to plaque antigens may be significantly different from that mediated by peripheral blood lymphocytes. Gingival crevice lymphocytes may also be more susceptible to serum elements which can modify CMI. The objectives of the proposed study are to compare CMI in response to plaque antigens between gingival crevice lymphocytes and peripheral blood lymphocytes as measured by proliferative and cytotoxic responses and to test the effect of antigen, antibody, and antigen-antibody complexes on these responses. Lymphocytes isolated by an atraumatic washing technique from the gingival crevice and lymphocytes isolated from peripheral venous blood will be tested for blastogenesis in response to plaque antigens as measured by cellular uptake of 3H-thymidine. The ability of each lymphocyte population to lyse 51Chromium-labeled chicken red blood cells (CRBC) after plaque antigen stimulation will be tested. Gingival crevice leukocytes will also be tested for their ability to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) of rabbit anti-CRBC-treated, 51Cr-labeled CRBC'S. Using salt fractionation, column chromatography, ultrafiltration, affinity chromatography, acrylimide gel electrophoresis, and immunoelectrophoresis, preparations of antigen, antibacterial antibody, and immune complexes will be isolated from human serum and rabbit antibacterial serum. These compounds will be tested for their ability to modify the in vitro assays of CMI and ADCC mediated by both gingival crevice and peripheral blood lymphocytes.